Patent GB-235824-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-04-07
Abstract: 235,824. Coventry Automatic Telephones, Ltd., and Collyer, J. E. April 7, 1925. Automatic exchange systems.-A common impulse machine and translating frame are provided for a number of register-controllers of the code-translating type. Terminals on the frame for which no digit is to be sent are left unconnected, the stepping on of the transmitting sequence switch being looked after by the impulse machine. The machine impulses go direct to a relay in the relay group from which the register-controller was seized. Provision is made for releasing the register-controller if dialling is delayed and for routing the call to operators in response to the dialling of O or of an unobtainable route code. Accidental impulses prior to dialling are absorbed. In case the numerical code is to be received by a number indicator, transmission is held up until an idle one is available (the register-controller being released however if the delay is excessive). The talking connection switches may be of the type described in Specification 218,789, but the invention is described with reference to a system using Strowger switches. A subscriber A, Fig. 1, is connected by his line switch B to a relay group C associated with a group selector D and a switch E for selecting an idle register-controller F. Impulses from the common machine G operate a relay in the group C through the common frame H tor the route code and direct for the numerical code. The call goes over selectors D, V, a repeater K and selectors and connector L, M, N. Line switch, Fig. 2. Line relay 1 completes a self-interrupting circuit over normal terminal 4 for the stepping magnet 8, and when an idle relay group is found, cut-off relay 9 extends the loop Selection of idle register-controller. Relays 51. 53, Fig. 3, pull up and a self-interrupting circuit is made for the magnet 57 of switch E over its wiper 61. When an idle register-controller is found, relay 56 being no longer shortcircuited connects 'battery to wiper 64, energizes relay 69 and releases relay 53. Relay 67 locks up and holds the line switch after relay 53 falls back. Registration of route code. Relay 151, Fig. 4, pulls up over wiper 64 and energizes relay 153 which returns ground over dialling tone transformer 155 to relay 56 which is thus held up and functions as a transformer. Dialled digits are repeated by relay 51 to relay 151 which controls digit registers R1 - - R4 in succession over wiper 161 of a back-stroke drive register sequence switch S the stepping magnet 170 of which is energized at the beginning and released at the end of each digit by a relay 163. The first energization of relay 163 energizes relay 166 which locks up, replaces the dialling wire by earth, and starts the common impulse machine over wire 216 if it is not already running. In the third position of switch S, relay 172 pulls up over wiper 173 and completes a self-interrupting circuit for the stepping magnet 175 of the register M. This is a 25- point back-stroke, drive rotary switch with twelve single-ended wipers in two diametrically opposite sets of six, so as to be in effect a six-wiper, 50- point switch. The terminals are arranged in groups and the switch sets itself under control of the bridged wipers 178 to a group determined by the setting of register R1 and then to a set within the group determined by the joint setting of the registers R2, R3. When the group is reached, the driving circuit is opened by relay 182 which pulls up over wipers 181, 178 to ground at 180. When the switch S moves to its fourth position, relays 172, 182 fall back and relays 186, 189 pull up, the latter locking up. A further circuit is thus completed for magnet 175 which steps the switch M until relay 182 finds a circuit over wiper 194, wiper 178 and wiper 192 of the registers R3, M2, R2 respectively, and locks up. Registration of remaining digits. In the fourth position of switch S, the first digit of the numerical code is received by the register R4. The operation of relay 163 connects ground from 173 over contacts of relay 186 to the off-normal wipers 200, 204, 208 of the registers R1 - - R3 which return to normal and are re-set in succession by the remaining digits. Transmission of route code. The common impulse machine comprises a number of cams or drums and associated wipers 1 - - 10<1>, Fig. 6, whereby battery is connected to a number of busbars from one to ten times in 1¢ seconds, a certain fixed pause being provided between trains. The energization of relay 182 when the register M is set energizes the magnet 223 of the transmitting sequence switch T over wiper 301 and the grounded are 305 of the impulse machine, and when wiper 301 leaves the arc the switch takes a step and connects the impulse relay 75 in the relay group, Fig. 3, over wiper 221 of the register M and the common translating frame F to one of the bus-bars. Each rotation of the machine causes the switch T to take another step. If fewer than four digits are to be sent, the terminals corresponding to the missing ones are left unconnected. Transmission of numerical code and release of the register-controller. In the fifth and later positions of switch T, the impulse relay is connected to the proper bus-bars over wipers 227, 229 &c. of the registers R4, R1 - - B3. After the final digit, wiper 238 of switch T moves on to a dead terminal and relay 153 falls back, and unlocks relay 166 and also relay 56 in the relay group, Fig. 3. Restoring circuits over their offnormal banks 241, 250 are made for the switches S, T. When the switch S reaches normal a circuit is made for restoring the register R4 over 173, 245, 246, 247. Register R4 on reaching normal extends the circuit to restore the register R1. The successive restoration of R2 and R3 is effected in a similar manner. The register-controller can be seized again as soon as relay 153 falls back. Preventing sending from overtaking dialling. If at any stage the switch T overtakes the switch S a circuit is made over wipers 173, 254 for relay 172 which disconnects the stepping magnet 223 and cuts the impulse circuit. Relay 172 is held over its lower winding after switch S has moved or until the machine has finished sending a train. Release of register-controller if dialling is delayed. A common interrupter 257 grounds wire 258 for a second or two every fifteen seconds. Two-step relay 259 pulls up its armature 262 at the beginning of the first impulse after the energization of relay 153 and its other armature when the impulse ends. The next impulse thus shortcircuits relay 153 to release the register-controller unless relay 259 has been released in the interval by the response to dialled impulses of relay 151. Connection to operator by dialling O. Register R1 brings its wiper 264 on to the terminal 265 and relay 266 cuts the dialling circuit and starts the register M, which hunts for the terminal marked over wiper 181. The required code is sent out from this position, the switch T being operated in a circuit 212, 269, 214, 305. Relay 266 disconnects terminal 272 and after 4 steps of the switch T relay 153 falls back to release the register-controller. Unobtainable numbers. A first digit 1 is absorbed as described later. If the second and third digits give with the first an unobtainable route code, the switch M fails to find a stopping place in the group to which it was set in accordance with the first digit, and is arranged to stop on the first terminals of the next group. This is provided for by the multipling between the banks of wipers 264, 181 of the register R1. If for example the first digit is 3, the wipers 178 pause on terminal 183, and failing to find a marked set in the group are stopped on terminal 184 by the energization of relay 182 in a circuit 266, 264, 184, 275. These (eight) positions are multipled and route the call to an operator or cause a special tone signal to be given. Absorbing accidental impulses. If register R1 makes only one step the switch S is restored to normal by self-interruption in a circuit 170, 241, 278, 266 and completes the restoring circuit for register Rl. Delaying transmission of impulses to a number indicator. The fact that a number indicator is not yet ready is indicated by a reversal of the current flowing on the trunk and the resulting energization of relay 99, Fig. 3. This completes a circuit for relay 172 which prevents further transmission, as described in a previous paragraph. Relay 172 puts an alternative ground on wiper 61 to keep the register-controller busy if the delay is such that the timing arrangement releases it. Primary selector, Fig. 3. The first digit of the route code operates the vertical magnet 77 and relay 86 in parallel. The change-over of springs 80 energizes stepping relay 87 and causes the relapse of relay 86 at the end of the digit, whereupon the rotary magnet 78 steps the switch and unlocks relay 87. Magnet 78 and relay 87 continue to interact until an idle line is found, whereupon the switching relay 93 being no longer short-circuited pulls up in series with relay 87, extends the talking and private wires, and short-circuits the upper winding of relay 56 to give a balanced impedance for talking. Incoming selector, Fig. 7, and repeater, Fig. 8. Relays 401. 405. 408 and 411 pull up. Relay 401 repeats the digit to vertical magnet 414. The change-over of off-normal springs 409 causes the relapse of relay 408 at the end of the digit. Rotary magnet 420 gives the wipers a step and releases the stepping relay 411. The stepping relav and magnet 420 interact until an idle repeater is found, whereupon switching relay 423 releases relays 401, 405. Relays 451, 453 in the repeater pull up, the former repeating the remaining digits. Relay 456 is not operated as its windings are in opposition. The energization of relay 459 at the beginning of each digit puts a non-inductive shunt across the impedance 458 an